The present invention relates to a baling press and to a method of operating a baling press.
To facilitate storage, handling and transportation of loose material, such as waste paper and cardboard, waste plastic, straw, it is usual to press the material into bales.
To prepare the bales, the material is compressed in a baling press. A baling press typically includes a bale pressing channel in which a pressing ram is reciprocally movable to and fro, new material to be baled being added each time after the press has been retracted. The counter pressure against which the bales are pressed is obtained by resistance encountered by the material as it is pressed through the pressing channel, which, to that end, has a cross-section that decreases in downstream direction over at least a portion of its length. Initial counter pressure may be obtained by mounting obstacles in the pressing channel.
For facilitating separation of the pressed material into distinct bales and for keeping the bales together, string material is usually tied around the bales. The string material is for instance wire or rope material. The wire material is for instance steel or plastic wire and the rope material is for instance plastic or natural fiber material that may be twisted or braided and include one or more strands of twisted fiber material. A number of loops of the string extending around the bale is usually obtained by feeding strings from two sources along opposite sides of the bale to be formed, tying the strings together near the downstream end of the bale to be formed and tying together the strings near the upstream end of the bale after the material for forming that bale has been pressed.
Tying together the strings is usually accomplished by twisting or twining end sections of the wire material from a mutually parallel configuration as is for instance described in U.S. Pat. No. 3,667,377 or by tying ends of rope material to each other as is for instance described in European patent application EP 2 941 951.
For passing the string from one side of the bale pressing channel to an opposite tying side where it is to be tied to the string fed from that tying side, loop supply members in the form of rods having a loop supply member at a distal end are provided. An example of such a loop supply member is described in more detail in U.S. Pat. No. 5,255,597. Each time after a bale is pushed out of the pressing chamber, the loop supply members are extended via slots in the pressing ram and passages in walls of the pressing channel, catch the strings at the side opposite the tying side and are retracted to pull the strings over to form a temporary loop projecting until out of the pressing channel. During retracting movement, the loop supply members also entrain the string into temporary loops so that the temporary loops of strings from both sides commonly extend along the loop supply members so that the strings can be tied to each other.
In particular when compressing relatively wet and/or fine material, the slots in the baling press and in the passages in the walls of the pressing channel for allowing the loop supply members to pass through tend to become clogged up, to such an extent that reliable binding of the bales is no longer ensured.
In German patent applications 2 523 043, 3 939 944 and 3 036 562, European patent application 0 492 260, it is proposed to close off the slots in the pressing rams. U.S. Pat. No. 4,604,858 proposes a stationary probe that passes through grooves in the pressing ram when the pressing ram moves to its retracted position. U.S. Pat. No. 4,092,913 proposes that loop supply members push material out of the slots when extended to pick up string material. U.S. Pat. No. 3,084,619 proposes movable closing plates that close off ports in walls of the pressing channel.